Glass fiber-plastic composites of improved strength



Dec. 29, 1970 A. MARZOCCHI 3,551,

GLASS FIBER-PLASTICQCOMPOSITES OF IMPROVED STRENGTH Filed March 6, 1967ATTORNEYS United States Patent 015cc 3,551,269 Patented Dec. 29, 19703,551,269 GLASS FIBER-PLASTIC COMPOSITES OF IMPROVED STRENGTH AlfredMarzocchi, Cumberland, R.I., assignor to Owens- Corning FiberglasCorporation, a corporation of Delaware Filed Mar. 6, 1967, Ser. No.620,694 Int. Cl. D02g 3/18, 3/36; D03d 15/00 US. Cl. 161-93 7 ClaimsABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The presentinvention relates to composites of the type wherein a plastic isstrengthened or reinforced by glass fibers; and especially to suchcomposites wherein the glass fibers are present in the form of a wovenfabric.

In the Biefeld Patent 2,650,184, there is described a composite whereina fabric of glass fibers reinforces a resin. The patent is directed to amethod of improving the tear strength of such a composite by producing apartial or poor bond of the resin to the cloth. The patent appears toteach a composite wherein the plastic is forced down into the fabric insuch a manner that the plastic does not fill all of the interstices ofthe fabric. The patent also appears to teach that improved tearresistance is had when the cloth is treated so that a poor bond is hadbetween the resin and the fabric. The patent appears to also teach thatbecause of the poor bond between the plastic and the cloth, the strandsof the cloth are free to shift when a tear stress is applied thereto toprevent the plastic from concentrating shear on the individual fibers.

It has been found, however, that the materials of the Biefeld patent donot provide optimum strength and the concentrated loads cause the fibersto spread. Because of the weak attachment, stress applied to one fiberis not properly transmitted to another fiber through the plastic. Inaddition, the plastic does not provide total separation between thefibers so that flexing may produce abrasion of the fibers under certainconditions.

SUMMARY OF THE INVENTION The present invention relates to a composite ofglass fiber yarns surrounded by plastic with the yarn comprising atleast two strands of glass fibers twisted together with sections of oneof the twisted strands being of greater length than the section of theother twisted strand which it overlays to thereby provide fiber loopswith plastic extending around the fiber loops.

The principal object of the present invention is the provision of a newand improved composite having improved abuse resistance.

A further object of the invention is the provision of a new and improvedcomposite of the above described type wherein the plastic bonds tofibers of each strand so that the plastic is capable of transferringforce from one fiber to another fiber, and so that breakage of some ofthe fibers do not proportionally decrease the strength of the composite.

Further objects and advantages of the invention will become apparent tothose skilled in the art to which it relates from the followingdescription of several preferred embodiments described with reference tothe accompanying drawing forming a part of this specification.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary sectional viewthrough a composite of glass fibers and plastic and which embodiesprinciples of the invention;

FIG. 2 is a cross sectional view similar to FIG. 1 showing anotherembodiment of the invention; and

FIG. 3 is a plan view of the woven glass fibers shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The composite 10 shown in FIG.1 generally comprises a woven fabric formed of multi-strand yarn 14 ofglass fibers, and which yarn is surrounded by a stretchable plastic 16.Yarn 12 is formed of two strands which are twisted together. One of thestrands 20 comprises 408 monofilaments of E glass having a diameter ofapproximately 0.00025 inch. The other strand 22 likewise comprises 408monofilaments of E glass of the same diameter, but the monofilaments ofthe strand 22 are separated in a manner similar to what is sometimescalled texturizing. In addition to being texturized the monofilaments ofthe strand 22 are longer than are the monofilaments of the strand 20.The excess length of the monofilaments of the strand 22 form loops 24which extend around the strand 20.

The yarn arrangement of the invention will provide increased strengthwhen formed into composites with any type of resin, be it thermosettingor thermoplastic. Because thermoplastic resins, and particularly thosehaving great stretchability, produce composites which tear easily, thereinforcing arrangement of the present invention will have particularadvantages when reinforcing these stretchable resins. Suitablethermoplastic resins will include cellulose esters, including celluloseacetate, cellulose butrate or the like, cellulose ethers such as ethylcellulose, benzyl cellulose, or nitro cellulose, polystyrene 3 orchlorinated polystyrene, acrylic esters, vinyl acetate, vinyl alcohol,vinyl chloride, vinyl acetals, copolymers of vinyl acetate and vinylchlorides, polyvinylidene chloridevinyl chloride copolymers, polybutene,polyethylene, polychloroprene, butadiene acrylonitrile copolymers,polyesters, polyurethanes, the various natural and synthetic rubbers,silicones, etc.

Example 1 A woven fabric was made using 40 warp yarns per inch and 44weft yarns per inch. Each yarn was made of two 408 filament strands, themonofilaments of which were made of E glass and had a diameter of0.00025 inch. The yarn was texturized at the time the strands weretwisted together and during which time one strand was overfed at a rateof 3 percent while the other strand was overfed at a rate of 70 percent.As the strands were twisted together and during the overfeedingoperation, they were passed through an air jet which filamentized thestrand that was overfed by 70 percent, into individual or small groupsof filaments. By overfed is meant the feeding of the yarn to the air jetat a positive rate in excess of the rate which withdrawal rolls removethe yarn from the air jet.

The yarn which was processed as above described was coated with aconventional starch lubricant. The fabric after being woven was heatcleaned to remove the starch coating and provide a set to the weave. Byheat cleaning is meant a process wherein the fabric is heated in air ata temperature of approximately 900 F. to 'burn off the organicmaterials.

The heat cleaned fabric was then coated with a A; inch layer of a creamyemulsion having the following composition:

Ingredients: Percent product by weight Emulsion50% solids, comprising80% methamethacrylate, 20% vinylacetate 50 Water premix, 50% polyacrylicacid 5 Ammonium hydroxide (2830% NH l Gammamethacryloxy propyltrimethoxysilane 1 Water Remainder The coated fabric was dried at a temperature ofapproximately 212F. The fabric was turned over, and a A; inch thicklayer of the same material was applied to the other side which was alsodried in the oven at approximately 212 F. After being coated on bothsides, the coated fabric was passed between calender rolls havingsurfaces heated to approximately 300 F., whereby the coatings were fusedand pressed around the fibers to completely embed the fibers in theplastic.

The material made as above described has abuse resistance that isconsiderably improved over a conventional fabric made of untexturizedyarn of the same filament count and of the same warp and weft count. Itwill be seen that the loops of the filamentized strand allow the plasticto become embedded between the filaments to totally and permanentlyseparate the filaments and thereby prevent mutual abrasion. In addition,the plastic which permeates the filaments is greatly strengthened by thefilaments to form a high strength region of the plastic having astrength and tear resistance considerably greater than that of theunreinforced plastic. The high strength regions formed by the plasticand impregnated loops distribute concentrated loads to the strand aboutwhich the loops are formed, as well as to the yarn which extends atright angles to the plastic impregnated loop. A concentrated loadapplied to the strand which is surrounded by the loop, causes thesurrounded strand to become bowed to pull portions of the strand fromeither side of the concentrated load towards the concentrated load.Because the untexturized strand has plastic tightly bonded thereto byreason of other loops on either side of the concentrated load, theplastic is caused to grow towards the concentrated load, and therebybuild up the amount of plastic which resists the pressure of theconcentrated load.

By way of contrast, the prior art composites are thinned out in theregion of a concentrated load to either leave the glass fibers exposedto the load, or to produce a rubbing action of the fibers against eachother.

Shear forces applied to the edges of the composite of the presentinvention are also resisted by the high strength regions of the plasticthat are formed by the plastic impregnated loops to thereby distributethe shear forces over a greater area of the strands. This reduces theangle at which the filaments of the strand are bent, and as is wellknown in the art, glass fibers are easily broken when they are bent attoo sharp an angle.

In the above composition, the gammamethacryloxy propyltrimethoxy silaneis a coupling agent which improves the attachment or bond of the resinto the fibers. Instead of mixing this material with the coatingcomposition, it can also be applied as a pretreatment by dipping thefabric into a l to 5 percent solution, prior to the application of acoating material which does not include the coupling agent.Alternatively, an advantage will be had in some instances by applyingthe coupling agent only to the strand which is overfed by the greatestamount in the yarn forming operation to further enhance the bond of theresin to the looped fibers. This will not be necessary in mostinstances, however, because of the good physical bond which is achievedwith the filamentized strand. Even nonheat cleaned starch size strandswhen filamentized will be satisfactory for most instances because of thegood physical bond that is achieved with the filamentized strand. Thesolution may be either an organic solution, or in some instances, awater solution.

Example 2 A preferred type of yarn is shown in FIG. 2. The yarn of FIG.2 is formed by twisting two 408 filament strands together. Each strandis formed by filaments of E glass having a diameter of approximately0.00025 inch. Each of the strands are overfed by 10 percent during thetime that they are passed over an air jet which alternately filamentizesor texturizes the strands. Both strands of the yarn are texturized atalternately spaced positions as seen in FIG. 2. A fabric of thismaterial was made using 40 warp and 40 weft yarn per inch, followingwhich the fabric was heat cleaned in the above described manner.

A plastisol of the following composition was prepared:

Ingredients: Parts by weight Particulate polyvinyl chloride resin (highM.W.) Diisodecylphthalate 40 EDioctylphosphite 20 'Epoxidized soya oil7.5 Titanium dioxide 5 Lead phosphite 3 Vinyl trichloro silane 2 Thecomposite is prepared by applying a inch layer of the above material tothe fabric of Example 2, and thereafter the material would be fused at atemperature in the range of 200-250 F. Thereafter, /8 inch layer isapplied to the opposite side of the fabric and it is also is fused at atemperature of 200-250 F. The coated fabric is then passed throughbetween heated rolls having a surface temperature of from 200-250 F. tothoroughly fuse the polyvinyl chloride material together and encase thefiber. A plan view of the fabric before coating is shown in FIG. 3.Those portions of the fabric shown in FIGS. 2 and 3 which correspond tosimilar portions of the fabric shown in FIG. 1 are designated by a likereference numeral characterized further in that a suffix a is afiixedthereto.

It will be seen that both strands of a yarn of the fabric of Example 2contain filamentized loops and that these loops are alternately spaced.The pattern of these loops is shown in FIG. 3, and these loops formreinforced areas of plastic having a strength and a modulus considerablygreater than the portions of the plastic which are not reinforced by thefilaments. It will be seen that the strands of the yarn shown in FIGS. 2and 3 are all anchored by filamentized loops whereas one strand in theyarn of the fabric shown in FIG. 1 is not filamentized and its anchorageis dependent upon force transferred from the filamentized loops to theunfilamentized strand.

When a concentrated load is applied to the fabric of FIGS. 2 and 3,loops on opposite sides of the concentrated load provide completeanchorage, so that plastic in the immediate vicinity of the concentratedload is progressively pulled towards the load as the force is applied.There is, therefore, a marked build up of stretchable plastic in thearea of the concentrated load which in turn distributes the load ontothe fibers running in both directions.

Instead of the vinyl trichloro silane being mixed with the plastisolcomposition, an organic solution thereof can be formed using one partvinyl trichloro silane and 99 parts toluene. Fabric can be dipped intothe solution, or the solution can be otherwise applied to the fabric andthe silane coated fabric dried at a temperature from 150- 250 F. Theplastisol mixture with or without an organosilane can then be applied.

Example 3 A formable composition was prepared from the followingingredients:

Ingredients: Parts by weight Polyvinylchloride emulsion polymerizedresin (normal molecular weight) 50 Polyvinylchloride emulsionpolymerized resin (low molecular weight) 50 Dioctyl phthalate 20Diisodecylphthalate 50 Calcium carbonate filler l Sb O fire retardant 5Lead phosphite 5 Polyethylene glycol 2 Kerosen diluent -15Azobisformamide blowing agent 5 RHB pigment 3-10 This material wasprepared by adding the pigments to the plasticizer in a Hobart mixer.The fillers and fire retardants were mixed with another part of theplasticizer in a small mixer and then blended into the Hobart mixer.Thereafter, 100 parts of the normal and low molecular weight polyvinylchloride powders were added to the Hobart mixer and blended togetherfollowing which the diluent and ethylene glycol were added. Thismaterial is applied to both sides of the fabric of Example 2 and thenfoamed in situ by passing through an oven heated to 300 F. to foam thecomposition in situ. The filamentized loops are firmly embedded in thefoam plastic and this composite has greately improved strength over acomposite similarly formed except that the fabric used is a conventionaluntexturized one having the same fiber filament content.

Example 4 Parts by weight Oil extended butadiene-styrene rubber (SBR-Prebroken smoked sheet natural rubber (65 Mooney) Zinc oxide 3 Stearicacid 1 Carbon black 50 Pine tar 5 Diphenylamine-acetone reaction product(Aminox) '1 Diphenylguanidine (DPG) .2

N cyclohexyl 2 benzothiazolesulfenamide (Santocure) 1 Sulphur 1.75

The oil extended butadiene-styrene rubber and the smoked sheet naturalrubber is cut up into small pieces and fed to a Banbury mixer that isrun at slow speed. After one minute of mixing, half of the carbon black,the zinc oxide, the stearic acid, and the diphenylamine-acetone reactionproduct is added and mixed for one minute. Thereafter, the remainder ofthe carbon black and the pine tar are added and mixed for two and onehalf minutes, following which theN-cyclohexyl-Z-benzothiazolesulfenamide, the diphenylguanidine and thesulphur are added and mixed for a minute and a half. The compound atthis stage is thoroughly blended and is then dumped from the Banburymixer. The rubber compound is then cut up into small pieces and droppedinto a container of toluene which is continually agitated by a paintstirrer or other mixer to form a solution containing about 33 percent byweight solids. The fabric of Example 2 is coated with the above mixturein two stages, the first of which works the mixture into the fabric, andthe second of which provides a top dressing of approximately /a inchthick. This material is then dried in an oven at approximately 200 F.following which the opposite side is coated in the same manner. Sheetsof this material are then cured in a press at a temperature of about 350F. until vulcanization is completed. The composites so formed hasconsiderably greater abuse resistance than does a composite similarlyformed of a fabric of like fiber and yarn count, differing only in thatthe yarn does not contain the filamentized loops, but is of aconventional strand. v

From the above description, it will be apparent that both solid and/orfoamable coatings can be applied to the fabric to provide solid or foamresin matrixes which are reinforced by the fibers. A coupling agent,such as an organosilane need not be used in all instances since thefilamentized loops provide good mechanical anchorage without the use ofa coupling agent. Where a coupling agent is used, however, more thanapproximately 0.5 percent based on total solids is necessary to producea demonstrable effect, and more than 5 percent will not provide anappreciable improvement in most instances. For many instances,satisfactory results will be achieved using uncoronized starch sizedstrand without a coupling agent, either applied directly to the fibersor with the impregnating resin. This is because of the good mechanicalanchorage Which is achieved with the filamentized loops. The aboveexamples show that improved tear strength is achieved even when theresin is applied to both sides of the fabric to thoroughly surround thefibers. It will be apparent that the synergistic effect is also achievedWhere the impregnating resin is applied to only one side of the fabric.From the above description, it will also be apparent that the glassfiber reinforcing need not be woven, but can be in the form of a matformed by yarns containing the texturized loops above described. Stillfurther modifications of the invention will occur to those skilled inthe art, and it is my intention to cover hereby all novel adaptations,modifications, and arrangements thereof which come within the practiceof those skilled in the art to which the invention relates and whichfall Within the purview of the following claims.

I claim:

1. A composite of glass fiber yarn surrounded by plastic, said yarncomprising at least two strands of glass fibers twisted together, atleast one of said strands having been subjected to an air jet treatmentso as to filamentize the strands into individual filaments or groups offilaments and both of said strands being overfed to the twistingoperation by at least approximately 3% to cause each strand to have alength greater than that of the yarn, said yarn being embedded inplastic.

2. The composite of claim 1 in which said yarn comprises one of themutually perpendicular yarns of a woven fabric.

3. The composite of claim 1 in which said yarn comprises both of themutually perpendicular yarns of a woven fabric.

4. A composite of glass fiber yarn surrounded by plastic, said yarncomprising at least two strands of glass fibers twisted together, atleast one of said strands having alternate sections that have beentexturized by an air jet treatment so as to separate the sections intoindividual filaments or groups of filaments separated by generallyuntexturized sections, and both of said strands being overfed to thetwisting operation by at least approximately 3% to cause each strand tohavea length greater than that of the yarn, said yarn being embedded inplastic.

5. The composite of claim 4 wherein both strands are alternatelytexturized and untexturized.

6. The composite of claim 5 wherein the texturized portions of bothstrands are alternately spaced.

References Cited UNITED STATES PATENTS 10 ROBERT F. BURNETT, PrimaryExaminer R. L. MAY, Assistant Examiner US. Cl. X.R.

7. The composite of claim 5 wherein the yarn is in the 15 153; 161-475form of a woven fabric.

